In this activity (on page 2 of the PDF), learners will develop their own version of a tool used by biologists, a dichotomous key, by collecting all their left shoes. Learners brainstorm different characteristics and decide how to divide the pile into two groups with a common characteristic. A chart should be made as they continue to divide each group in two until each shoe has its own group. Learners use the chart to identify each person's shoe. Relates to the linked video, DragonflyTV GPS: Cactus.